Re: [PATCH] null_blk: Always split BIOs to respect queue limits

[Damien Le Moal <dlemoal@kernel.org>]

On 1/26/24 16:05, Hannes Reinecke wrote:
> On 1/26/24 01:50, Damien Le Moal wrote:
>> The function null_submit_bio() used for null_blk devices configured
>> with a BIO-based queue never splits BIOs according to the queue limits
>> set with the various module and configfs parameters that the user can
>> specify.
>>
>> Add a call to bio_split_to_limits() to correctly handle large
>> BIOs that need splitting. Doing so also fixes issues with zoned devices
>> as a large BIO may cross over a zone boundary, which breaks null_blk
>> zone emulation.
>>
> That feels so wrong. Why would we need to apply queue limits to a bio?
> (Yes, I know why. We still shouldn't be doing it.)

Splitting is at least needed for zoned devices. Otherwise, everything breaks
with the zone emulation.
> Maybe indeed time to kill the bio-based path.

I have nothing against that :)

> 
> But until that happens:
> 
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> 
> Cheers,
> 
> Hannes

-- 
Damien Le Moal
Western Digital Research